Plasmonic nanoparticles and metasurfaces to realize Fano spectra at ultraviolet wavelengths

We discuss the possibility to realize sharp Fano scattering signatures in the ultraviolet (UV) range, based on dipolar scattering of nanoparticles. At these frequencies, material losses usually do not allow sharp resonant effects, hindering plasmonic applications based on higher-order multipolar modes, like conventional Fano resonances. We propose to excite degenerate scattering states supported by core-shell nanoparticles made of a sapphire core and an aluminum shell. We predict enhanced, highly confined fields, supporting sharp far-field scattering signatures from single nanoparticles and planar arrays of them. These results may lead to the design of UV filters, photodetectors, sensors, and energy-harvesting devices

Boosting Optical Nonlinearities in Є-Near-Zero Plasmonic Channels

The anomalous transmission properties of zero-permittivity ultranarrow channels are used to boost Kerr nonlinearities and achieve switching and bistable response for moderate optical intensities. Strong field enhancement, uniform all along the channel, is a typical feature of ε-near-zero supercoupling and is shown to be particularly suited to enhance nonlinear effects. This is obtained by designing narrow apertures at cutoff in a plasmonic screen. We show that this nonlinear mechanism can significantly outperform nonlinearities in traditional Fabry-Pérot resonant gratings

Nonlinear Plasmonic Cloaks to Realize Giant All-Optical Scattering Switching

Here we extend the reach of Fano resonant coupling by combining this concept with cloaking and plasmonic resonances in a single nonlinear nanoparticle, in order to realize giant all-optical scattering nanoswitches controlled by moderate pumping intensities. We show that a core-shell nonlinear plasmonic particle may be designed to abruptly switch from being completely cloaked to being strongly resonant, with up to a 40 dB cross-sectional difference. Self-tunable optical cloaks and resonant scatterers are envisioned for use as efficient all-optical switches and nanomemories

Broadband Brewster transmission through 2D metallic gratings

Recently, we have introduced a mechanism to achieve ultrabroadband light funnelling and total transmission through 1D narrow metallic gratings at a specific incidence angle, the so-called plasmonic Brewster angle. This phenomenon is based on impedance matching between the guided modes supported by ultranarrow linear slits and transverse-magnetic waves at oblique incidence. In this paper, we demonstrate that such phenomenon, representing the equivalent of Brewster transmission for plasmonic screens, can also occur in 2D metallic gratings of various structural forms and shapes, and that it may be made insensitive to the azimuthal, or polarization, angle u. This finding may have relevant implications to realize large funneling, absorption and squeezing of light in perforated metallic screens

Plasmonic nanoparticles and metasurfaces to realize Fano spectra at ultraviolet wavelengths

We discuss the possibility to realize sharp Fano scattering signatures in the ultraviolet (UV) range, based on dipolar scattering of nanoparticles. At these frequencies, material losses usually do not allow sharp resonant effects, hindering plasmonic applications based on higher-order multipolar modes, like conventional Fano resonances. We propose to excite degenerate scattering states supported by core-shell nanoparticles made of a sapphire core and an aluminum shell. We predict enhanced, highly confined fields, supporting sharp far-field scattering signatures from single nanoparticles and planar arrays of them. These results may lead to the design of UV filters, photodetectors, sensors, and energy-harvesting devices

Nonlinear Plasmonic Cloaks to Realize Giant All-Optical Scattering Switching

Here we extend the reach of Fano resonant coupling by combining this concept with cloaking and plasmonic resonances in a single nonlinear nanoparticle, in order to realize giant all-optical scattering nanoswitches controlled by moderate pumping intensities. We show that a core-shell nonlinear plasmonic particle may be designed to abruptly switch from being completely cloaked to being strongly resonant, with up to a 40 dB cross-sectional difference. Self-tunable optical cloaks and resonant scatterers are envisioned for use as efficient all-optical switches and nanomemories

Boosting optical nonlinearities in e-near-zero plasmonic channels

The anomalous transmission properties of zero-permittivity ultranarrow channels are used to boost Kerr nonlinearities and achieve switching and bistable response for moderate optical intensities. Strong field enhancement, uniform all along the channel, is a typical feature of ε-near-zero supercoupling and is shown to be particularly suited to enhance nonlinear effects. This is obtained by designing narrow apertures at cutoff in a plasmonic screen. We show that this nonlinear mechanism can significantly outperform nonlinearities in traditional Fabry-P´erot resonant gratings

Matching and funneling light at the plasmonic Brewster angle

The ultrabroadband impedance matching of metallic gratings at the plasmonic Brewster angle [A. Al`u et al., Phys. Rev. Lett. 106, 123902 (2011)] is analyzed here in several realistic scenarios and configurations, and in the case of nonmonochromatic excitation. This phenomenon is the analogy of the well-known Brewster transmission for dielectric slabs but, when applied to plasmonic gratings, has the remarkable property of funneling and concentrating light within subwavelength slits. We analyze here how the presence of absorption and of realistic substrates and/or superstrates may influence the phenomenon, its beamwidth and angular selectivity, and its overall performance in the case of broadband, ultrashort incident pulses in the time domain. We prove that broadband signals may be concentrated and transmitted almost unaffected through narrow apertures, even in the presence of absorption, very different from conventional extraordinary optical transmission based on resonant phenomena

Broadband Brewster transmission through 2D metallic gratings

Recently, we have introduced a mechanism to achieve ultrabroadband light funnelling and total transmission through 1D narrow metallic gratings at a specific incidence angle, the so-called plasmonic Brewster angle. This phenomenon is based on impedance matching between the guided modes supported by ultranarrow linear slits and transverse-magnetic waves at oblique incidence. In this paper, we demonstrate that such phenomenon, representing the equivalent of Brewster transmission for plasmonic screens, can also occur in 2D metallic gratings of various structural forms and shapes, and that it may be made insensitive to the azimuthal, or polarization, angle u. This finding may have relevant implications to realize large funneling, absorption and squeezing of light in perforated metallic screens